The use of computers, especially personal computers (PCs) is widespread. A PC includes a number of individual components, such as a microprocessor, memory modules, various system and bus control units, and a wide variety of data input/output (I/O) devices. The components included in a PC require electrical power for operation. Significant amounts of energy may be wasted in the event one or more of the PC components is not used while maintained in a powered-up state. This can be particularly disadvantageous for portable notebook computers, which rely on batteries for their power. In order to provide more energy-efficient PCs, power management techniques and circuitry have been developed which place one or more of the PC components into a powered-down state at appropriate times. For example, a particular I/O device may have an associated device timer which tracks the time elapsed since the last activity of the I/O device. After a predetermined time interval has elapsed, with no I/O device activity, the I/O device is put into a powered-down state. Similarly, there exist system mode timers which track the time elapsed since any user interaction or other selected event occurs with the PC generally. For example, a typical notebook computer can successively enter states or modes of progressively lower power consumption until a user interaction or other selected event occurs. Typical computers have states such as Full-On, Standby or Doze, Sleep, Deep Sleep or Suspend, and Off.
One disadvantage of current art power management systems is that significant energy may still be wasted during those idle time periods prior to the PC entering the lower power consumption modes. A second disadvantage is that a PC, once in a low power consumption mode, may be slow to respond to subsequent user interaction with the PC. For example, if the system is in the Suspend mode, the video display monitor may be completely unpowered. To transition to Full-On may require several seconds for the display to function. If instead the system or video display monitor were in the Standby mode, a transition to Full-On will be much quicker. Current systems and techniques for power management in PCs are less than optimal in balancing the need to maximize both power conservation and system responsiveness to user interaction.